Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnly, idempotent, openWorld and non-destructive, and the description adds genuinely new behavioral context: the upstream authority (US VHA MED-RT via NLM RxClass), the fact that results are a reference list rather than label warnings, and a cost of 1 credit. It does not cover edge behavior such as what is returned for an unknown or ambiguous drug name.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The scope statement and example are front-loaded and the caveats are grouped at the end, so the agent hits the essential information first. It is somewhat over-stuffed for a single-parameter lookup, with the 'students, carers and agents' audience sentence and the pharmacist/prescriber disclaimer being the weakest-value content.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a one-parameter read-only lookup with no output schema, the definition supplies source provenance, a sample of returned fields (conditions plus MeSH IDs), and clear scope limits. The only meaningful gap is return-shape specifics such as what an empty or unmatched result looks like.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

With one parameter at 100% schema description coverage, the schema already documents 'name' as a generic or brand drug name with an example, so the baseline is 3. The description's 'via ... (e.g. metformin: ...)' reinforces the example but adds no new guidance on brand vs generic matching or ambiguity handling.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ('Lists the medical conditions a drug is recorded as contraindicated with'), names the underlying reference (MED-RT via RxClass), and gives a concrete example (metformin: Renal Insufficiency, Liver Diseases, Acidosis). The framing 'Who should not take this drug?' plus the explicit contraindication scope separates it cleanly from siblings like drug_listed_uses or drug_pharmacologic_class.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives positive context ('useful for students, carers and agents doing a first-pass reference check') and exclusions ('not the full warnings in a product label; drug-drug interactions are not covered'), which tells an agent when this tool is the wrong choice. It stops short of naming the sibling tools that would cover warnings or interactions, so routing is implied rather than explicit.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.